On 11/30/22 21:57, Rob Clark wrote: > From: Rob Clark <robdclark@xxxxxxxxxxxx> > > drm_gem_shmem_mmap() doesn't own this reference, resulting in the GEM > object getting prematurely freed leading to a later use-after-free. > > Link: https://syzkaller.appspot.com/bug?extid=c8ae65286134dd1b800d > Reported-by: syzbot+c8ae65286134dd1b800d@xxxxxxxxxxxxxxxxxxxxxxxxx > Fixes: 2194a63a818d ("drm: Add library for shmem backed GEM objects") > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx> > Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> > --- > drivers/gpu/drm/drm_gem_shmem_helper.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c > index 35138f8a375c..3b7b71391a4c 100644 > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c > @@ -622,10 +622,8 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct > } > > ret = drm_gem_shmem_get_pages(shmem); > - if (ret) { > - drm_gem_vm_close(vma); > + if (ret) > return ret; > - } > > vma->vm_flags |= VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP; > vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); AFAICS, the dmabuf mmaping code path needs a similar fix, isn't it? - /* Drop the reference drm_gem_mmap_obj() acquired.*/ - drm_gem_object_put(obj); vma->vm_private_data = NULL; - return dma_buf_mmap(obj->dma_buf, vma, 0); + ret = dma_buf_mmap(obj->dma_buf, vma, 0); + + /* Drop the reference drm_gem_mmap_obj() acquired.*/ + if (!ret) + drm_gem_object_put(obj); + + return ret; -- Best regards, Dmitry
